Can't Delete vmdk file

I have a VM that is no longer needed. It's been powered down and removed from inventory, but I can't delete the vmdk file. I've deleted every other file associated with the VM except the vmdk. I get the error below when trying delete it from WinSCP

General failure (server should provide error description).

Error code: 4

Error message from server: Failure

Request code: 13

I get the error below when trying to delete it from command line

rm: cannot remove `boxi-flat.vmdk': Device or resource busy

I've tried renaming the file, but no luck. I found every process that was in use with the VM name in it and killed it.

Does anyone know how I can delete this?

Thanks,

Scott